Tool for metal cutting

ABSTRACT

A tool for cutting metal machining comprises one or several cutting insert seats (1), each one for an indexable cutting insert, each insert seat comprising a bottom support surface (10) and at least two side surfaces, which form a right angle with each other. One of these side surfaces comprises two side surfaces (12, 16), which are located at different distances from the bottom support surface (10), one of these being intended as a support surface for square cutting inserts and the other as a support surface for specially shaped hexagonal inserts. In this way, one and the same insert seat can accommodate either a square or a hexagonal cutting insert, which considerably improves cutting economy.

The present invention relates to a tool for cutting metal machiningaccording to the preamble of claim 1. More specifically, the inventionrelates to a tool that makes possible a fastening of indexable cuttinginserts with different numbers of cutting edges in one and the sameinsert seat.

The use of detachable, indexable cutting inserts is nowadays commonpractice for generally all cutting metal machining, i.e. for turning,milling, boring, etc. They are usually made of coated or uncoatedcemented carbide, but some ceramic materials also occur. These differentindexable cutting inserts may have very varying geometrical basicshapes, depending upon cutting economy and applications. They may e.g.be triangular, rhombic, square, rectangular, round, hexagonal andoctagonal. Further, they may be double-sided or single-sided, dependingon if cutting edges are present on both sides or only one side.

Common for all possible different insert shapes is that they require aninsert seat in the holder per se adapted to the shape of the insert.Thus, square inserts normally require an insert seat with two mutuallyperpendicular support or bearing surfaces in the insert seat, a roundinsert requires a round support surface, or at least segments of such asurface, an insert with the shape of a regular hexagon necessitates twosupport surfaces that are angled by 120° to each other (or two surfacesat a distance that are angled by 60° to each other), etc. This meansthat a change of insert shape also requires a change of holders. This istime-consuming and, primarily, expensive.

The advantage with, e.g., a hexagonal insert in comparison with a squareone, is of course that the hexagonal one has more cutting edges, moreprecisely for a single-sided insert, two more. Naturally, this involvesa better cutting economy, since by one and the same insert, one inprinciple may extend the working time by 50%. However, somedisadvantages with hexagonal cutting inserts is that they do not makepossible the same cutting depth as for instance square inserts do (i.e.,inserts with the same extension from the middle point to the operativecutting corner), and that they do not make possible 90° milling orturning. Therefore, it is desirable or necessary to sometimes replacefor instance square cutting inserts, whereby also the holder has to bereplaced, as mentioned above.

For instance, in U.S. Pat. No. 4,966,500 holders are disclosed fordifferent basic shapes of cutting inserts, such as square, hexagonal andoctagonal. It may easily be understood that square and octagonal insertscould be fitted into the same insert seats, since both these havecutting edges located perpendicularly to each other. However, hexagonalinserts require their own holders, which may be seen in that citation.

Thus, a first object of the present invention is to improve the cuttingeconomy by optimizing the number of cutting edges in one and the sameholder.

A second object of the present invention is to provide an insert seatthat may accommodate both square and hexagonal inserts.

Another object of the present invention is to provide a hexagonal insertthat may fit in an insert seat for square inserts.

These and further objects have been achieved in a way that is surprisingfor the skilled man, by constructing a cutting insert seat and a cuttinginsert, respectively, with the features as defined in the claims 1 and5.

For illustrative but non-limiting purposes, some preferred embodimentsof the invention will now be further described with reference to theappended drawings.

These are herewith briefly presented:

FIG. 1 shows an exploded view of an insert seat according to theinvention, in a perspective obliquely from above.

FIG. 2 shows an exploded view of a somewhat modified insert seataccording to the invention, in perspective obliquely from above.

FIG. 3 shows the same insert seat as FIG. 1, but with a hexagonal insertinstead of a square one.

FIG. 4 shows the corresponding insert and insert seat as FIG. 3, howeverwithout a shim.

FIG. 5 shows the bottom side of a hexagonal insert according to theinvention, in a perspective obliquely from above.

FIG. 6 shows the same insert seat as FIG. 2, but with a hexagonal insertinstead of a square one.

FIG. 7 shows the corresponding insert and insert seat as FIG. 6, howeverwithout a shim.

FIG. 8 shows the bottom side of another embodiment of a hexagonal insertaccording to the invention, in a perspective obliquely from above.

FIG. 9 shows a milling cutter body with cutting insert seats accordingto the invention according to FIG. 1, a square and a hexagonal inserthaving been mounted.

FIG. 10 shows a milling cutter body with insert seats according to theinvention according to FIG. 2, a square and a hexagonal insert havingbeen mounted.

In FIG. 1 a cutting insert seat according to the invention is generallydesignated by reference numeral 1. As may be seen in FIG. 9, this insertseat is located in a milling cutter body 2, but in principle it may alsobe placed in, e.g., a boring bar or a drill tip. Basically, the cuttinginsert seat consists of a bottom support surface 10 and two sidesurfaces 40 and 41, which are substantially perpendicular to each other.In this insert seat is mounted an indexable cutting insert 3, whichaccording to FIG. 1 has a square basic shape. In order to protect themilling cutter body against any possible insert breakdown, the insert 3rests upon a shim 4, which normally is also made of cemented carbide.The shim is fastened in the insert seat 1 by an internally andexternally threaded shim screw 5, which is tightened into the threadedhole 6 of the insert seat by means of a hexagon key that fits into thehexagonal hole 7. Thereby, the bottom surface of the shim will bearagainst the bottom support surface 10 of the insert seat. Moreover, theshim bears against the side support surface 14; on the other hand, itusually does not reach the other, lower side surface of the insert seat,in this case the rounded surface 13. According to the exemplifiedembodiment, the surface 14 consists of a planar surface and the surface13 of a boring with a sector-shaped cross-section. The central hole ofthe shim is formed with an abutment shoulder 8, against which theunderside of the head of the shim screw 5 abuts. The locking screw 9 isthreaded into the inner thread of the shim screw 5 and, thereby, itlocks the insert 3, the bottom side of the insert pressing against thetop surface of the shim. The head of the locking screw 9 is providedwith a recess for tightening, e.g., a so called torx recess 37. When theindexable cutting insert 3 is fastened in the insert seat 1, it willbear against the axial support or abutment surface 11 and the radialsupport or abutment surfaces 12A and 12B, respectively, which latter twoare located in the same plane. All these are angled to the bottomsurface 10 by substantially the same angle as the side or reliefsurfaces 52 of the insert are angled to the bottom surface of theinsert. Thus, the angle between said abutment surfaces and the normal ofthe bottom support surface is between 3 and 30°. Between the cuttingedges that are turned inwards and non-operative, and the surfaces abovethe abutment surfaces 11, 12, is a gap, so that these cutting edges arenot damaged. These two gaps 42 and 43 may be seen in FIG. 9.

In FIG. 3 the same insert seat is illustrated as in FIG. 1, but with ahexagonal insert 15 mounted instead of the square insert 3. Thus, theother included machine elements are identical. When this insert isfastened in the insert seat, it will abut on one hand against the axialabutment surface 11, thus against the same surface as the square insertin FIG. 1 abuts against, and on the other hand against the support orabutment surfaces 16A and 16B, which are located in one and the sameplane. This plane is substantially plane-parallel to the plane ofabutment surfaces 12A, 12B and located somewhat farther away from theaxis of the center hole 6, than the latter plane. Between on one handthe surfaces 12A, 12B, and on the other hand the surfaces 16A, 16B, isprovided a transition shoulder 39. The surfaces 12A, 12B and 16A, 16B,respectively, are separated from each other by means of a substantiallystraight milled-out recess 17. This recess need not per se intersect thesurface 16, but nevertheless it contributes favourably to providing astatically well-defined two-point abutment radially.

In order to make a cutting insert with the shape of a regular hexagonfit into the insert seat, it should be shaped so that it comprises thefeatures as shown in FIG. 5. The bottom side of the insert has the shapeof a dodecagon, and it may be brought to be regular, but preferably itis defined by alternating somewhat shorter and somewhat longer edges 19Aand 19B, respectively.

According to the embodiment shown in FIG. 5, the side surfaces 15 of theinsert, which hence extend between the bottom surface 18 and the topsurface or chip surface, are shaped in a way that will now be describedfurther. From each part edge 19A starts a surface portion 20, whichfirst forms a tapering portion 23, that tapers substantially in the formof a trapezoid or an isosceles frusto-triangle, into a narrower waistportion 21, and then it widens again in the direction of the chipsurface, whereby it forms an abutment surface 22, which is intended tobear against the abutment surface 16A, 16B. The intersection linebetween the abutment surface 22 and the top side of the insert form amain cutting edge 30. It should be pointed out that the part of theabutment surface 22 situated adjacent the main cutting edge 30 doessuitably not come in contact with the support surfaces 16, in order notto damage said edge when it has been indexed inwardly in the insertseat. Thus, as may be seen in FIG. 9, the six-edge insert 15 protrudesfrom the upper delimiting lines of the insert seat (i.e., the upperdelimitation line of the support surfaces 16). Suitably, the surface 20is somewhat convexly curved at the waist portion 21, which may be seenleft-most in FIG. 4. Thereby the main cutting edge 30 is strengthened onthe relief side, in order to withstand larger cutting forces. If thiswould not be considered necessary, the knick point at the waist portioncould be deleted, whereby the whole "spatulate" surface 20 is in onesingle plane. For small cutting forces, even an inversion of the waistportion would be feasible, i.e., the waist portion 21 would exhibit aconcave radius, corresponding to the radii 25 described below.

Between the surface portions 20, the cutting insert has intermediateportions 24, which have a hexagonal basic shape that is curvedsubstantially along the connection line between two opposed corners.This curving forms a concave radius surface 25. That part of theintermediate portion 24 that adjoins a part-edge 19B constitutes anabutment surface 26, which may be brought to bear against the axialsupport surface 11. However, suitably, the whole abutment surface 26 isnot intended to bear against the support surface 11. More specifically,the part of the surface 26 situated adjacent the edge 19B will notcooperate with said support surface, but rather the part located nearerthe radius surface 25. The transition surface 27 protruding from thecenter of the insert constitutes a free-surface, whose width decreasesfrom the radius surface 25 in the direction of the chip surface of theinsert. Between this transition surface and the chip surface there is aparallel land 28, whose secondary land cutting edge 29 generates asmooth surface on the workpiece, in a manner known per se. In thetransitional region between the appurtenant abutment surface 22 and theparallel land 28, there is preferably a transition surface 31, whicheither is planar or has a radius. Further, this surface 31 is somewhatmore inclined in relation to the normal of the bottom surface than isthe abutment surface 22, in this way allowing for a sufficient clearancebehind the cutting edge of the parallel land (axially).

A characteristic, combinatory double effect of the present invention isrealized by the existence of on one hand the recess or milled-out recess17 in the one support surface of the insert seat, and on the other handthe "spatulate" surface portion 20 on the hexagonal cutting insert 15.By shaping the former sufficiently broad and the latter sufficientlynarrow at the waist portion 21, said waist portion may be fitted intoand go free from the recess 17, and thus be countersunk between thesupport surface portions 12A, 12B. Thereby, the feature characteristicfor the present invention is achieved, that support surfaces ondifferent levels may be used for different insert shapes.

Above the axial support surface 11 there is an elongated intermediatesurface 36, which is located substantially on the same height from thebottom support surface 10 as the support surfaces 16A, 16B. Thisintermediate surface 36 is to be considered as a mere free-surface,without any contact to a mounted cutting insert.

In FIGS. 1 and 3 (and also in FIGS. 2 and 6) embodiments are illustratedcomprising a shim 4. However, this is not an essential feature of thepresent invention, which also comprises constructions without such ashim. Such a one is shown in FIG. 4. The only difference between thisfigure and FIG. 1 and 3 is that the bottom support surface 10 protrudesby a height difference corresponding to the thickness of the shim. Thisbrings about the advantage per se that the material thickness in theinsert-carrying protrusion 32 becomes thicker and, thereby, stronger.

As may be best seen in FIG. 1, one or several of the support surfaces11, 12 and 16 may be provided with sparing surfaces 33, 34 and 35,respectively. These are arranged so that the side edges shall not becapable of causing intrusions in the insert seat, thereby damaging it inthe long run.

FIG. 9 shows a milling cutter body with six identical cutting insertseats, which are shaped to correspond the embodiment according to FIG. 1and 3. In the figure, two of these are equipped, one with an indexablecutting insert of a square basic shape and one with an indexable cuttinginsert of a hexagonal basic shape. However, this is not a combinationthat is used for a real machining step, but is to be seen as a mereillustration of the basic concept of the present invention.

According to the illustrated embodiments, the support surface 11, thatis common for the two insert types, is the axial support surface.However, it may easily be realized that the locations of the sidesurfaces may be converted, whereby the support surface 11 would becomethe radial support surface and the support surfaces 12 and 16 axialsupport surfaces.

FIG. 2 and the appurtenant FIGS. 6, 7, 8 and 10 show an embodiment ofthe invention that is somewhat modified relative to FIG. 1.Corresponding details have been designated with the same referencenumerals as in the corresponding FIGS. 1, 3, 4, 5 and 9. One differencebetween FIG. 9 and 10 is that in FIG. 10 only onecutting-edge-protecting gap (gap 42) exists, which is located betweenone of the non-active cutting edges of the insert, being directedinwardly, and the surface above the abutment surfaces 12.

In FIG. 6 is illustrated the same insert seat as in FIG. 2, but with ahexagonal cutting insert 15' mounted, instead of the square insert 3.Thus, the other included machine elements are identical. When thiscutting insert is fastened in the insert seat, it will bear on one handagainst the axial abutment surface 43, and on the other hand against thesupport or abutment surface 16. The plane of the surface 16 may besubstantially plane-parallel with the planes of the abutment surfaces12A, 12B and located somewhat farther from the axis of the center hole6, than the latter plane. The angle of the plane 16 to the normal of thebottom surface 10 can be somewhat smaller than the angle of thecorresponding abutment surface 22 on the insert, which in principlepermits a linear abutment between the cutting insert and the upperdelimitation line of the abutment surface 16. The level of saiddelimitation is determined by the formation of the milled-outfree-surface 49.

In order to make a cutting insert of a regular hexagonal shape fit intothis insert seat, it shall be formed so that it comprises the featuresas depicted in FIG. 5 or 8. The cutting insert according to FIG. 5 hasalready been described above. However, by the somewhat modified insertseat according to FIG. 2, it will rest in a somewhat different way, asdescribed below.

In combination with FIG. 2, the surfaces 22 are intended to abut on onehand against the abutment surface 16 (or against its upper delimitationline) and on the other hand against the abutment surface 43, which areangled substantially by 120° to each other. As mentioned above, the partof the abutment surface 22 located adjacent the main cutting edge 30should not come in contact with the support surface 16, in order not todamage said cutting edge when it has been indexed inwardly into theinsert seat. Of the same reason, there is preferably a free-surface 44above the abutment surface 43. However, the surface 44 is not necessary,cf. FIG. 7.

According to FIG. 1, that part of the intermediate portion 24 thatadjoins a part-edge 19B constitutes an abutment surface 26, which isbrought to abut against the same axial abutment surface as the squarecutting insert. Admittedly, this brings the inconvenience that theinsert has to be ground considerably, since abutment surfaces usuallyhave to be ground. According to FIG. 2, only the circumferential,cutting-edge-adjacent surfaces 22 function as abutment surfaces, whichmakes the insert considerably more easily ground.

The cutting insert according to FIG. 8, whose bottom surface has theshape of a substantially regular hexagon with rounded corners, isdescribed below.

According to FIG. 8, the spatulate surface 20 has been replaced by anabutment surface 22', a transition surface or free-surface 50 that isangled inwardly towards the center of the insert, and a free-surface 23'extending between surface 50 and the bottom surface of the insert. Thebottom surface 18' has the shape of a regular hexagon with roundedcorners. Between two adjacent free-surfaces 23', there are providedrounded radius surfaces 51, which in principle replace the intermediateportions 24 in FIG. 5. The parallel lands 28' and the transitionsurfaces 31 ' correspond to details 28 and 31, respectively, in FIG. 5.According to this embodiment, the transition surfaces 50 areconsiderably angled towards the center of the insert, so that they, andalso the free-surfaces 23', do not come in contact with the facingsurfaces in the insert seat, in first hand the surfaces 12 and 14, and11, 15 and 46, respectively. Also this embodiment has the endeavouredfeature, that all side abutment surfaces of the insert (i.e., thesurfaces 22') are located at the top, along the cutting edges, whichmakes the cutting insert easy to grind.

Between the axial support surface 11 for square inserts and the roundsurface 13, there is a free-surface 45. At the opposed side of thesupport surface 11, there is arranged a transition surface 46, which issubstantially plane-parallel with the bottom supports surface 10.Between this one and the support surface 43 for hexagonal inserts,extends another transition surface 47, which forms an obtuse anglerelative to both surfaces 43 and 46. Adjacent to the surfaces 43, 44 andat the same distance as those from the bottom support surface 10, thereis a free-surface 48. As may be easily understood, the hexagonal insertaccording to FIG. 8 and the insert seat are mutually so shaped, that theinsert goes free from all surfaces below the support surface 43, i.e.surfaces 13, 45, 11, 46 and 47, and of course also from the laterallyarranged surface 48.

Furthermore, according to the illustrated embodiments the indexablecutting inserts have been provided with a through central hole 38 forthe fastening by a locking screw. However, this has nothing to do withthe ingenious location of the support surfaces in the insert seat,wherefore also other clamping arrangements are feasible, such as acenter pin or a lever pin, and also such constructions that do notrequire any central hole in the insert, e.g. a wedge or a pressingclamp.

We claim:
 1. Tool for cutting metal machining comprising at least onecutting insert seat for accommodating at least one indexable cuttinginsert, the at least one insert seat including a bottom support surfaceand at least two side surfaces, the at least two side surfaces forming asubstantially right angle with each other and include support surfacesadapted to bear against the cutting insert mounted in the insert seat,one of the at least two side surfaces including at least two supportsurfaces, the at least two support surfaces being located at differentdistances from a plane of the bottom support surface, one of the atleast two support surfaces being shaped to support cutting inserts of asubstantially square basic shape and another of the at least two supportsurfaces being shaped to support cutting inserts of a substantiallyhexagonal basic shape.
 2. Tool according to claim 1, wherein anotherside surface of the at least two side surfaces has at least one supportsurface being shaped to support both cutting inserts of a substantiallysquare basic shape and cutting inserts of a substantially hexagonalbasic shape.
 3. Tool according to claim 1, wherein at least the supportsurface for the insert of a substantially square basic shape is dividedinto two part support surfaces by a recess.
 4. Tool according to claim1, wherein the at least two support surfaces on one of the at least twoside surfaces are substantially plane-parallel.
 5. Tool according toclaim 1, wherein the support surface for the insert of a substantiallyhexagonal basic shape is divided into two part support surfaces by arecess.
 6. Tool according to claim 1, wherein the support surface forthe insert of a substantially square basic shape is divided into twopart support surfaces by a recess, the recess also dividing the supportsurface for the insert of a substantially hexagonal basic shape into twopart support surfaces.
 7. Tool according to claim 1, wherein the atleast two support surfaces on one of the at least two side surfaces aresubstantially plane-parallel, the support surface for the insert ofsubstantially hexagonal basic shape being located at a larger distancefrom a middle point of the bottom support surface than the supportsurface for the insert of a substantially square basic shape.
 8. Toolfor cutting metal machining comprising at least one cutting insert seatfor accommodating at least one indexable cutting insert, the at leastone insert seat including a bottom support surface and at least two sidesurfaces the at least two side surfaces forming a substantially rightangle with each other and include support surfaces which are adapted tobear against the cutting insert mounted in the insert seat, the at leasttwo side surfaces each including at least two support surfaces locatedat different distances from a plane of the bottom support surface of theat least two support surfaces being shaped to support cutting inserts ofa substantially square basic shape and another support surface of the atleast two support surfaces being shaped to support cutting inserts of asubstantially hexagonal basic shape.
 9. Tool according to claim 8,wherein the support surface for the insert of a substantially squarebasic shape is divided into two part support surfaces by a recess. 10.Indexable cutting insert of a substantially hexagonal basic shape forcutting metal machining comprising a bottom surface, a top or chipsurface, and a configuration of side surfaces extending therebetween,the configuration of side surfaces including at least six first abutmentsurfaces, each abutment surface of the at least six first abutmentsurfaces being located proximate a main cutting edge, and theconfiguration of side surfaces including at least six second abutmentsurfaces located proximate an intersection line of the configuration ofside surfaces with the bottom surface.
 11. Indexable cutting insertaccording to claim 10, wherein the intersection line between the bottomsurface and the configuration of side surfaces describes a dodecagon.12. Indexable cutting insert according to claim 10, wherein a center ofeach first abutment surface of the at least six first abutment surfacesis disposed substantially midway between two succeeding second abutmentsurfaces of the at least six second abutment surfaces.
 13. Indexablecutting insert of a substantially hexagonal basic shape for cuttingmetal machining comprising a bottom surface, a top or chip surface, anda configuration of side surfaces extending therebetween, theconfiguration of side surfaces including at least six first abutmentsurfaces, each abutment surface of the at least six first abutmentsurfaces being located proximate a main cutting edge, and theconfiguration of side surfaces including at least six second abutmentsurfaces located proximate an intersection line of the configuration ofside surfaces with the bottom surface wherein each first abutmentsurface of the at least six first abutment surfaces forms part of acorresponding first surface portion of a plurality of first surfaceportions, and each second abutment surface of the second abutmentsurfaces forms part of a corresponding second intermediate surfaceportion of a plurality of corresponding second intermediate surfaceportions, each intermediate surface portion of the plurality of secondintermediate surface portions being located between two of the firstsurface portions.
 14. Indexable cutting insert according to claim 13,wherein a land is disposed between two first abutment surfaces of the atleast six first abutment surfaces and a second intermediate surfaceportion of the plurality of second intermediate surface portions. 15.Indexable cutting insert according to claim 13, wherein the firstsurface portions include a waist portion having a convex radius, andthat a second intermediate surface portion has a concave radius. 16.Indexable cutting insert according to claim 15, wherein the secondintermediate surface portion has a substantially hexagonal basic shape,the concave radius extending between two opposed corners of thehexagonal basic shape.
 17. Indexable cutting insert of a substantiallyhexagonal basic shape for cutting metal machining comprising a bottomsurface, a top or chip surfaces, and a configuration of side surfacesextending therebetween, the configuration of side surfaces including atleast six abutment surfaces, each abutment surface of the at least sixabutment surfaces being located proximate a main cutting edge, and atleast six other surfaces which are unground and are disposed proximatean intersection line of the configuration of side surfaces with thebottom surface.
 18. Indexable cutting insert according to claim 17,wherein, underneath each abutment surface, a transition surface isdisposed and is angled downwards-inwards toward a center of the cuttinginsert, and wherein, below the transition surface, a free-surfaceextending to the bottom surface of the cutting insert is disposed. 19.Indexable cutting insert according to claim 17, wherein each abutmentsurface of the at least six abutment surfaces forms part of a firstsurface portion of a plurality of first surface portions, and that eachother surface of the at least six other surfaces forms part of a secondintermediate surface portion, each second intermediate surface portionbeing located between two first surface portions of the plurality offirst surface portions.
 20. Indexable cutting insert according to claim17, wherein the intersection line between the bottom surface and theconfiguration of side surfaces describes a substantially regular hexagonwith rounded corners.
 21. Indexable cutting insert according to claim17, wherein a land is disposed between two abutment surfaces of the atleast six abutment surfaces.